Energy-Efficient Streaming Using Non-volatile Memory

The disk and the DRAM in a typical mobile system consume a significant fraction (up to 30%) of the total system energy. To save on storage energy, the DRAM should be small and the disk should be spun down for long periods of time. We show that this can be achieved for predominantly streaming workloads by connecting the disk to the DRAM via a large non-volatile memory (NVM). We refer to this as the NVM-based architecture (NVMBA); the conventional architecture with only a DRAM and a disk is referred to as DRAMBA. The NVM in the NVMBA acts as a traffic reshaper from the disk to the DRAM. The total system costs are balanced, since the cost increase due to adding the NVM is compensated by the decrease in DRAM cost. We analyze the energy saving of NVMBA, with NAND flash memory serving as NVM, relative to DRAMBA with respect to (1) the streaming demand, (2) the disk form factor, (3) the best-effort provision, and (4) the stream location on the disk. We present a worst-case analysis of the reliability of the disk drive and the flash memory, and show that a small flash capacity is sufficient to operate the system over a year at negligible cost. Disk lifetime is superior to flash, so that is of no concern

Analyzing the Trimming Activity of Solid-State Drives in Digital Forensics

The primary source for storing digital information has been remained constant for the last two decades, in the form of magnetic disks. However, a sudden shift has taken place in the data storage technology during the recent years where the transistor-based devices are being used as primary storage devices for storing complex data. There are many reasons due to which the manufacturers are shifting their platform from magnetic disks to solid state drives which uses transistor chips and this change is creating problems for the forensic investigators to investigate on the digital evidence. The deleted information can be easily retrieved from the hard disks by following specific guidelines, where as in solid state drives it is almost impossible to retrieve the lost data when TRIM command is enabled. SSDs can sometimes sanitize data all by themselves even if they are not connected to any interface. This paper gives an overview of the hard disks and solid-state drives for data recovery and mainly focuses on the functioning of TRIM command in solid state drives